KdVS is a disorder characterised by developmental delay and mild to moderate intellectual disability. Children with this disorder typically have a disposition that is described as cheerful, sociable, and cooperative. They usually have weak muscle tone (hypotonia) in childhood and about half have recurrent seizures (epilepsy).

KdVS is a multi-system disorder caused by disruption of the KANSL1 gene. The disorder has a prevalence of 1 in 16,000 worldwide and it is estimated to affect about 300 Australian children.

A greater understanding of the speech, language and reading deficits of KdVS may help to unravel the relevance of KANSL1 gene to child speech and language development.

MCRI's research co-author, Professor Angela Morgan, said that these findings that were published in The European Journal of Human Genetics will also help families and clinicians with prognostic counselling and the application of more targeted speech therapies for social, literacy and academic outcomes for children with KdVS. 

The team assessed individuals with KdVS aged from one to 27 years for oral-motor, speech, language, literacy and social functioning.

Speech was characterised by:

  • Apraxia - a motor speech disorder. Children have problems saying sounds, syllables, and words (100%)
  • Dysarthria - a condition in which the muscles you use for speech are weak or you have difficulty controlling them (93%)
  • Stuttering (17%)

In infancy they found that children had exceptionally low-tone and a high prevalence of gastro-oesophageal reflux, which was associated with feeding difficulties. 

Professor Morgan said that speech and language development was delayed on average to around two-and-a-half to three-and-a-half years of age.

"These children are highly sociable with a strong desire to communicate. As a result they keep practising speech even though it is really challenging for them to overcome the severe oral weakness in life that prohibits early speech development. They also tend to find powerful methods of communicating beyond spoken language (such as using electronic devices) because for some kids they can be as old as seven before they start to speak."

The study identified the need for greater understanding and expression of language, particularly in relation to their peers.

"Our study also highlighted the critical need for speech therapy and non-verbal communication such as sign language to support kids with KdVS particularly while they are in preschool," Professor Morgan said.

Professor David Amor, a clinical geneticist at MCRI and co-author of the study, said that although KdVS cannot be cured, these new insights into speech and language problems in children with KdVS will lead to better treatments that will improve communication and enhance the quality of life of the children and their families.

Madilyn's story

Kathy Hunt's daughter, Madilyn was one of the first people in Victoria to be diagnosed with KdVS. She was non-verbal until the age of around six when she started speaking a few words. Madilyn is now 15 and while she does have difficulty with some pronunciation and clarity, she is now quite competent verbally.

Madilyn's mum, Kathy said that they now struggle to stop her from talking. "It is interesting to note also she now speaks quite well and often, her speech regresses when she is unwell or tired. She also loves to sing. Her singing lessons have now become her speech therapy."

The family were very keen to be a part of the study to assist in understanding the speech/language/communication difficulties associated with KdVS. Kathy said that sharing their experiences will help Speech Therapists help to provide the best possible strategies as new babies are diagnosed.

"There has already been a baby diagnosed before birth in Australia. That child has been able to receive targeted therapy from the very start, as opposed to us who just stumbled upon issue after issue until a diagnosis at 5 years at age, and even then there was little known."

"It's about giving children the best opportunity to reach their full potential - there is no greater gift than that," Kathy said.